// Copyright 2016 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_TRAP_HANDLER_TRAP_HANDLER_INTERNAL_H_
#define V8_TRAP_HANDLER_TRAP_HANDLER_INTERNAL_H_

// This file should not be included (even transitively) by files outside of
// src/trap-handler.

#include "src/trap-handler/trap-handler.h"

#include <atomic>

namespace v8 {
namespace internal {
    namespace trap_handler {

        // This describes a chunk of code that the trap handler will be able to handle
        // faults in. {base} points to the beginning of the chunk, and {size} is the
        // number of bytes in the code chunk. The remainder of the struct is a list of
        // protected memory access instructions and an offset to a landing pad to handle
        // faults on that instruction.
        struct CodeProtectionInfo {
            Address base;
            size_t size;
            size_t num_protected_instructions;
            ProtectedInstructionData instructions[1];
        };

        class MetadataLock {
            static std::atomic_flag spinlock_;

        public:
            MetadataLock();
            ~MetadataLock();

            // We'd normally use DISALLOW_COPY_AND_ASSIGN, but we're avoiding a dependency
            // on base/macros.h
            MetadataLock(const MetadataLock&) = delete;
            void operator=(const MetadataLock&) = delete;
        };

        // To enable constant time registration of handler data, we keep a free list of
        // entries in the gCodeObjects table. Each entry contains a {next_free} field,
        // which can be used to figure out where the next entry should be inserted.
        // In order to avoid having to initialize all the links to start with, we use
        // 0 to indicate that this is a fresh, never-used list entry and that therefore
        // the next entry is known to be free. If {next_entry} is greater than zero,
        // then {next_entry - 1} is the index that we should insert into next.
        struct CodeProtectionInfoListEntry {
            CodeProtectionInfo* code_info;
            size_t next_free;
        };

        extern size_t gNumCodeObjects;
        extern CodeProtectionInfoListEntry* gCodeObjects;

        extern std::atomic_size_t gRecoveredTrapCount;

        // Searches the fault location table for an entry matching fault_addr. If found,
        // returns true and sets landing_pad to the address of a fragment of code that
        // can recover from this fault. Otherwise, returns false and leaves offset
        // unchanged.
        bool TryFindLandingPad(uintptr_t fault_addr, uintptr_t* landing_pad);

    } // namespace trap_handler
} // namespace internal
} // namespace v8

#endif // V8_TRAP_HANDLER_TRAP_HANDLER_INTERNAL_H_
